The invention relates to a therapy for neoplasms which involves administration of the cytokine IP-10.
Recent studies of inflammation, growth control, and cell transformation have resulted in the definition of a novel superfamily of early response cytokines having homology to platelet factor 4 (PF4). These cytokines have immunomodulatory and growth regulatory properties. Expression of these proteins (to date at least ten different peptides have been identified) is induced in a wide variety of cell types by diverse inflammatory and mitogenic stimuli. The biological function of this burgeoning family of related proteins remains, however, largely unknown.
PF4 and .beta.-thromboglobulin (.beta.TG) were the first members of this family to be identified. They are alpha-granule platelet proteins that are released together during the platelet release-reaction. Both proteins are mediators of platelet effects in inflammatory and wound healing processes. PF4 is chemotactic for neutrophils and monocytes and has been shown to inhibit angiogenesis by preventing endothelial cell proliferation in response to growth factors. .beta.TG modulates connective tissue elements; it is chemotactic for fibroblasts, and an unprocessed form of .beta.TG containing four additional N-terminal amino acids is mitogenic for synovial cells and fibroblasts (reviewed in Wolpe, S. D. et al., The FASEB Journal 3: 2565-2573 (1989)).
Previously, IP-10 was isolated as the predominant mRNA induced by gamma-interferon (IFN.gamma.) in human monocytes (Luster, A. et al., Nature 315: 672 (1985)). IFN.gamma. is a glycoprotein secreted by activated T cells which, in addition to its antiviral properties, is a potent activator of the cellular immune response. IFN.gamma. activates macrophages, increases fibroblast and endothelial cell resistance to many non-viral pathogens, and modulates cell-surface proteins central to immune cell regulation. IP-10 (so named for induced protein of 10 kd) encodes a previously undescribed protein with approximately 30% amino acid identity to platelet factor 4 and interleukin 8 (Luster, A. D. et al., Nature 315: 672 (1985)). IP-10 is secreted from a variety of cells in culture (keratinocytes, endothelial cells, monocytes and fibroblasts) in response to IFN.gamma. (Kaplan, G. et al., J. Exp. Med. 166: 1098-1108 (1987)). In addition, IP-10 is expressed in vivo during the development of a cutaneous cellular immune response by keratinocytes, endothelial cells and infiltrating dermal mononuclear cells (Gottlieb, A. B. et al., J. Exp. Med. 167: 941-948 (1988)). IP-10 expression is seen in the epidermis and dermis in the cutaneous lesions of psoriasis (Gottlieb, A. B. et al., J. Exp. Med. 167: 941-948 (1988)) and tuberculoid leprosy (Kaplan, G. et al., J. Exp. Med. 167: 941-948 (1988)). The homology of IP-10 to chemotactic and mitogenic proteins suggests that it may play a role in the directed migration, activation and proliferation of both local and blood-borne cells that characterize the inflammatory response.
The similarities of the intron-exon structure of PF4 and IP-10 (Luster, A. D. et al., Mol. Cell. Biol. 7: 3723-3731 (1987)) and the fact that both genes map to the long arm of chromosome 4 (Luster, A. D. et al., Proc. Natl. Acad. Sci. U.S.A. 84: 2868-2871 (1986)) support the hypothesis that they evolved from a common ancestral gene by gene duplication. A remarkable number of new members of this family have recently been identified by studies that have isolated genes induced by various mitogenic or inflammatory stimuli or through the amino acid sequencing of secreted proteins in the media of activated cells (Wolpe, S. D. et al., The FASEB Journal 3: 2565-2573 (1989)). A comparison of the amino acid sequences reveals that the homology between the eight human proteins ranges from approximately 20% to 70%.
These cytokines have an overlapping, yet distinct, set of ascribed functions which include chemotaxis, mitogenesis, tumoricidal activity and cell activation. For example, neutrophil activating peptide, recently named interleukin (IL)-8, is secreted from monocytes, lymphocytes and endothelial cells stimulated by IL-2, tumor necrosis factor (TNF) and lipopolysaccharide (LPS) (Baggiolini, M. et al., J. Clin. Invest. 84: 1045-1049 (1989)). IL-8 is a potent chemoattractant for neutrophils and lymphocytes, it induces the respiratory burst and granule exocytosis of neutrophils, and, depending on its form, it either promotes or inhibits neutrophil adherence to endothelial cells (Baggiolini, M. et al., J. Clin. Invest. 84: 1045-1049 (1989)). Monocyte hemotactic peptide (MCP), however, is released from monocytes stimulated with IL-1, LPS and granulocyte-macrophage colony stimulating factor (GM-CSF) and from fibroblasts stimulated with platelet-derived growth factor (PDGF). MCP is only chemotactic for monocytes, and can augment the tumoricidal activity of human monocytes for several human tumor lines (Matsushima, K. et al., J. Exp. Med. 169: 1485-1490 (1989)). Furthermore, melanoma growth stimulatory activity, another member of this family that maps to the long arm of chromosome 4, is a known growth factor for melanoma cells and is induced in fibroblasts by PDGF and endothelial cells by IL-1, TNF and LPS (Richmond, A. et al., J. Cell. Physiol. 129: 375-384 (1986)).
Several years ago an assay was developed which allows one to screen a variety of secreted proteins to test their effects on tumor growth in vivo (Tepper, R. I. et al., Cell 57: 503-512 (1989)).